Electric motor unit



Oct. 3. 1933. iA. F. DORMEYER 1,928,965

ELECTRIC MOTORv UNIT Original Filed Dec. 23, 1929 4 Sheets-Sheet 1ln/ventola ggg if dnn, s

Oct. 3, 1933. A F, DORMEYER 1,928,965

ELECTRIC MOTOR UNIT Original Filed Dec. 23, 1929 4 Sheets-Sheet 2 f. x yil 555 @j /wq /Q a W l El llllllllll IIIIIIIIIA'IIII'IIIA 'lill YIIIIIII] 0d. 3, 1933. A, 5:- DORMEYER 1,928,965

ocr. 3, 1933. y A F, BORME-YER 1,328,965

ELECTRIC MOTOR UNIT Original Filed Dec.' 25. 1929 4 Sheets-Sheet fiPatented Oct. 3, 1933 UNITED STATES `Pivnanvr erica ELECTRIC MOTQR.lINl'E Albert F. Dormeyer, Chicago, Ill,

9 Claims..

- The present invention relates to electric motor units and isparticularly concerned with portable motor units for use upon varioushousehold appliances.

While the preferred embodiment which has been chosen to illustrate theinvention is a food mixer, the present motor unit is peculiarly adaptedto be utilized for all kinds of household appliances such as fruit juiceextractors, meat grinders, vegetable Slicers, cream whippers, fans,

massaging devices, door and furniture polishers, einery wheels,polishing wheels, etc., and `ie use described is to be regarded asexemplary of one of the many uses or" a portable power plant or motorunit which is universally applicable to household labor.

The food mixing devices of the prior art have not been provided withpower units having sunlcient range or iiexibility of power and speed.control lor performing the different linds of mixing or other-laborrequired ci such a device, and consequently, the prior devices were notadaptable to both high-speed and low-speed re quirements. For exarrple,the speed which is required for whipping cream or light liquids isvastly different from that required for mixing dough for bread, and thedevices of the prior art could not perform either or both ci. thesefunctions with the perfection or rapidity which is desirable in acommercially successivi machine.

Seine eiiort has been made to adapt V1g devices to different kinds ofwork by the use alternative gear ratios, but only a very limited numberof speeds could be secured by such an arrangement, and such devices arecomplicated, noisy, unwieldy and incapable of satisfactory performance.

The prior devices have also been too heavy, and too large to be handledconveniently by women, expensive, diflicult .to clean., and dinicult tooperate or control.'

One of the objects oi the present invention is the elimination of theforegoing difficulties cy the provision of an improved electric motorunit- :Eor household appliances having such a wide range of power andspeed control as to be adaptable to practically all kinds of householdlabor.

Another object is the'provision of a portable electric motor un'lt ofthe class described, which is light in weight, relatively small in size,and compact in construction, so that the device may be convenientlycontrolled and handled without physical effort, yet it includes a powersource of suilicient strength to perform all types of physi- (Cl. W32-36) cal household labor, and self-contained control.-

ling devices which make the portable machine adaptable to the manydifferent speed require ments for such labor.

Another object is the provision of a novel selie@ contained unit forhousehold appliances, which includes speed reduction devices to permitthe electric unit to operate at its most efficient speed, and speedcontrolling means to make the power unit capable of use with all kinds ohousehold es appliances having various speed requirements.

Another object is the provision o an iinproved electric motor unit lorportable householdl appliances, which is capable or beating, mashing,mixing, whipping, pulverizing or stirif@ ring wet or dry food productsor" every consist ency from thin liquids to thiol; batters or drymixtures, with a variable speed control for every different power orspeed requirement.

Another object is the provision of a portable electric motor unit forfood mixers and other household appliances which may be safely lettconnected for convenient use and control by means of a self-containedswitch located in the motor casing, and the paddles or which may besafely cleaned by running water while the tor is in operation.

mother object the provision oi an improved electric :notor or householdappliances, which provided with a irm and positive, yet quicklydetachable connecting device so that the motor unit may be safely andsecurely connected to an agitator unit to be supported by the same, butthe agitator unit may be readily removed lor cleaning and the motor unitmay be applied to many other types oi appliances.

Another object is the provision or an improved motor structure which iscapable of more economical manufacture and assembly and from. which allexcessive weight has been eliminated for the purpose of providing asmall power plant for household appliances which has a wider range ofadaptability and power, but which is peculiarly adapted to be made muchlighter than any of the motors of the prior art, so that it may bereadily handled by women without excessive physical effort.

Other objects and advantages ofthe inverttion will be apparent from thefollowing descrip tion and from the raccompanying drawings, in whichsimilar characters of reference indicate similar parts throughout theseveral views.

Referring to the drawings, of which there are four sheets;

Fig. 1 is an elevational view lustrating one of the uses of the presentelectric motor unit;`

Fig. 2 is a vertical, sectional view taken through the motor unit on aplane determined by the axis of the armature shaft with certain of theparts in elevation;

Fig. 3 is a horizontal, sectional view taken on the plane of the line3-3 of Fig. 2, looking in the direction of the-arrows;

Fig. 4 is a detail sectional view taken on a vertical plane through thebottom of the casing at the axes of the power shafts, with certain ofthe parts in elevation to show the structure of the power shafts;

Fig. 5 is a vertical, sectional view taken on the plane of the line 5--5of Fig. 2 with the motor and gear reduction mechanism shown inelevation.

Fig. 6 is a horizontal section taken on the plane of the line 6 6 ofFig. 5, showing the structure of the motor casing and the rheostat inplan.

Fig. 7 is a sectional view of the casing with the motor and rheostatremoved, taken on the plane of the line 7 7 of Fig. 5;

Fig. 8 is a sectional view through the motor -brushes taken on theplanel of the line 8 8 of Fig. 3, looking in the direction of thearrows.

The present application is a division' of my prior application, SerialNo. 416,927, filed December 23, 1929. for electric food mixers, and thepresent application is directed particularly to the electric motor unitwhich comprises one of the parts of the food mixer covered by the parentapplication.

Referring to Fig. 1, the present electric food mixer, which is indicatedin its entirety by the numeral 20, preferably consists of a separateagitator unit 21 and a separate motor unit 22. Both of these partscomprise unitary articles of manufacture, and the motor unit inparticular is capable of use as a power plant with many different typesof household appliances, of which the agitator unit or agitatorattachment is one example.

The present food mixer is preferably made portable in order to widen itsfield of utility and adapt the food mixer for use in mixing food in allkinds of household utensils.l While the present device is extremelysturdy and capable of long and efcient service, all excess Weight hasbeeneliminated by the provision of an improved structure, so that thecomplete mixer is so light that' very little effort is required on thepart of the user.

One of the primary purposes of the food mixer being to save physicaleffort on the part of the user, some of theobjects of the presentinvention would be defeated if excessive physical effort were requiredfor handling the mixer, and the present portable device possesses anadaptability and flexibility, in its application to various householdlabors, which was not present in the devices of the prior art.

In order to eliminate the necessity for constant attention to the foodmixer when the device is in operation or between successive operationswhen the agitator unit may be covered with the batter, or otheringredients which it is mixing, the mixer is preferably provided with astable supporting member, such as the agitator unit 21, which is adaptedto support the complete device in erect position under alarge variety ofdifferent conditions, one of which is illustrated in Fig. 1.

For this purpose, it is also desirable that the motor unit 22 beprovided with inherent balance and connected to the agitator unit21symmetrically so that the mixer is not overbalanced upon any side.

The agitator unit is shown in elevation in Fig. 1, and this unitpreferably includes a supporting member or plate 23, a guard indicatedin its entirety by the numeral 39, and one or more agitators 61. Thesupporting plate 23 forms a part of a positive and safe, yet quicklydetachable, connection between the agitator unit 21 and motor unit 22,and for this purpose, a supporting plate 23 is provided with a socket 24adapted to receive complementary male members or lugs 25 carried bymotor unit 22.

Referring to Fig. 5, it will be observed that the casing 40 of the motorunit 22 is provided at its bottom 41 with a projecting body 42 for thepurpose of securing the supporting plate 23 of the guard. The body 42 ispreferably complementary in cross-section to the socket 24 formed inplate 23, and in the present embodiment, both the socket 24 and body 42are made rectangular in shape.

The guard plate 24 is adapted to be received about the lugs 25 on thebase of the motor unit 22 and to be secured lthereto by a pair oftransverse screw bolts 45 passing through the guard plate 24 and throughthe lugs 25. The transverse bolts 45 provide a firm yet quicklydetachable connection between the motor unit 22 and any form ofhousehold appliance which is provided with a supporting plate 24.

The entire agitator unit may be readily removed from the motor unitwithout any mechanism such as gears or other parts that might be damagedby washing, and the agitator unit may be washed in the ordinary way ofwashing dishes, or -by running the food mixer with the agitator unit ina bowl of cleansing fluid, such as soap and water. All of the metalparts of the agitator unit are preferably plated with corrosionresisting metal, such as chromium. and the casing 40 for the motor ispreferably formed of a light aluminum alloy, capable of receiving afinish which is similar in appearance.

The electric motor unit 22 preferably consists of a unitary motor casing40, which encloses and protects the motor 86, a speed control device 87,and a speed reduction device 88. The exact shape of the casing 40 doesnot affect the merits of the invention, except that it is highlydesirable that the arrangement be light, and compact, and a veryefficient, sturdy and powerful motor unit is provided by the specificarrangement illustrated.

The motor unit is illustrated in full size in Figs. 2 to 8, and theentire mixer is so light that it may be handled without appreciablephysical effort, yet it is capable of performing many new functionsbesides all of the results which have been accomplished by the largeheavy and complicated mixing devices of the prior art.

In the present embodiment, the motor casing 40 is provided with asubstantially plane upper wall 89, front and rear walls 90, 91, whichare plane except for the provision of bearing sockets 92, a bottom wall41, which has already been described, and side walls 93, 94, which aresubstantially plane at their upper portions but curved inwardly adjacentthe bottom of the casing. The transversely extending grooves 95 formedin the side walls 93, 94 enhance the ornamental appearance of thecasing, and may also be employed as guides for receiving complementaryparts carried by a standard or other support (not shown).

The casing 40 is closed by means of a cover of vwall 41 of casing 40 mayY of bores 113, for receiving bushings which the front wall forms apart, the cover 104 also including a laterally extending flange 105,about the border of the front wall 90, the flange being adapted toregister with the top, bottom and side walls of casing 40. The flange105 is preferably recessed at 106, forming a relatively thin aligningflange 107, adapted to be received within the walls of casing 40 toalign the cover 104 with casing 40 and-definitely determine theassembled position of cover and casing.

The cover 104 may be secured to casing 40 by a plurality of screw -bolts108, 109, which pass through the cover, having their heads embedded incountersunk recesses 110, and having threaded ends engaging threadedbores which are formed in lugs 111, 112 carried within casing 40 by thewalls thereof.

Casing 40 is preferably provided with a pair of handles 96, one locatedon each of the side walls of the casing, and the handles 96 are prefnerably formed of electrical insulating material, such as a moldedphenolic condensation product, called bakelite. Handles/96 may be veryfirmly secured to the casing 40 by providing the upper end 97 of thehandle with a transverse groove 98 which is adapted to receive the uppercorner of the casing 40, so that the handle engages both the side wall94 and the top Wall 39.

The handle may be provided with threaded bores 99, 100, and secured tothe casing by screw bolts 101, 102, which pass through the walls ofcasing 40, and the upper screw bolt 101 is preierably provided with afrusto-conical nut 103 adapted to be received in the corner in theinterior of the casing, between the top wall '89 and side wall 94. Thehandle being drawn into firm engagement with both the top wall and theside Wall by the bolt 101, and being also secured by the bolt 102, thehandles are adapted to be rmly secured to the casing with a minimumamount of labor.

The handles 96 are also a great convenience for the housewife in themanipulation of the mixer since either hand may be used for steadyingthe mixer in pulverizing operations or other operations which requiresteadying, and the other hand may be used for controlling the speed ofthe motor.

The support or control of the device may be readily shifted from onehand to the other to enable the operatorto reach for ingredients oneither side, and if necessary both handles may be grasped in such mannerthat lthe motor unit may be held very firmly and a considerable amount vof force brought to bear upon the work where the motor is used for otheroperations than food mixing.

The speed yreduction mechanism 38 also forms a unitary part of the motorunit, being enclosed in the casing 40, and permanently secured thereto,so that no gears or other mechanism need be attached to the agitatorunit, and the operator need have no hesitancy about placing the agitatorunit in the water for washing' on accountI of gears or other mechanismsuch as are used in the. devices of the prior art.

Since the present agitator unit includes a pair of beater elements, themotor unit has been provided with a pair of drive shafts 34, 35, but itshould be understood that it is not necessary to utilizebotli of thedrive shafts when the motor is employed with other appliances. Thebottom be provided with a pair 32, 33, which form' bearings for shafts34, 35.

Referring to Fig. 4, it will be observed that each of the bushings 32,33 has an axial bore 114 forming the bearing, an annular flange engagingthe inside of the bottom wall 41, and a threaded portion 116 forengagement with an internally threaded cap 117.

The bearing structure of each of the drive shafts is substantiallyidentical, and consequently, only one of these structures need bedescribed in detail. The drive shaft 34 is ixedly secured at its upperend vto a combined bevel and spur gear 118, While the drive shaft 35 issecured in a similar manner to a spur gear 119, which is adapted to meshwith the teeth on the spur gear 118. All of the gears included in thepresent device may be made of cast metal and secured to the drive shaftsby casting the gear about one end of the shaft, or the gears may be madeout of fiber for the purpose of giving a more silent operation, in whichcase, the gears may be secured to the shaft by pins or other :fasteningmeans.

For the purpose of assembly, each of the drive shafts 34, 35, itsbearing and gear, preferably consist of a unitary assembly, which isheld together by the provision of an annular groove 120 formed in theshaft just below bushings 32, 33, and provided with a split ring 121 toprevent removal of the shaft from its bearing. .Washers may be placed oneither side of the split ring and an absorbent packing 122 carried inthe cap 117 is adapted to prevent leakage of oil out of the bore 123along the drive shaft. Each drive shaft assembly is also provided with aplate 124 coniined between the hub of its respective gear and thebearing 32, and rotation between the bearing 32 and casing 40 isprevented by a pin 125. The bearings 32, 33 may be provided with asupply of lubricant by a piece of absorbent felt 126, which is placed onthe bottom of the casing 40 about the annular anges 115 of the bearing,and secured in place by the plates 124.

1n order to provide a self-locating drive connection between theelectric motor unit and the two-element agitator unit, one of the driveshafts, such as shaft 34, is made substantially longer than the othershaft 35, so that the shaft 34 projects below shaft 35. Both of theshafts have non-circular ends, the non-circular formations extendingupward to a point within the bearing f caps 11'? on each shaft, and thecomplementary non-circular sockets 'l5 on tubular shafts 74 may be ofsucient length to receive either of the shafts, in order to securestandardization of parts.

The shafts 34, 35 are preferably provided with tapered portions 127 attheir lower ends for engagement with the upper ends of the tubularshafts '14 so that the tapered surfaces 127 are adapted to automaticallycam and rotate the tubular shafts '74 until they reach the properrotative position for engaging the non-circular ends 128 of shafts 34,35.

The provision of one shaft of greater length than the other enables theoperator to rst center and locate one of the beater elements on a shaft,after which the agitator may be rotated slightly upon the rst and longershaft to locate the second beater element upon the shorter shaft.

It will thus be observed that the present connection between the beaterunit and motor unit with a pair of shafts may be very readily and easilyaffected by the mechanism provided, and the agitator unit is quicklyattachable, as well as quickly detachable.

gta

The speed reduction mechanism 88 also includes a pinion 129 carried bythe armature shaft 130, a spur gear 131 rotatably mounted upon a shaft132, the spur gear being also provided with a bevel pinion 133 fixed torotate with gear 131. The rear wall 91 of casing 40 may be provided withan internally projecting lug 134, having a bore 135 which is inalignment with a bore 136 located in a similar lug 137 carried by cover104. Shaft 132 may have a knurled end 138, and may be provided with athrust bearing consisting of a collar 139 pinned to shaft 132. Theknurled end r138 -may have a drive fit in the bore 135, and the combinedspur gear and bevel pinion 131, 133, is rotatably mounted' on the shaft132 between collar 139 and lug 137 with suitable washers 140 tofacilitate proper meshing of the bevel gears. The drive shafts 34, 35are thus adapted to be rotated by the motor armature 141 through thefollowing train of gears; pinion 129 rotates spur gear 131, whichcarries bevel pinion 133, bevel pinion 133 rotates bevel gear 142 whichcarries spur gear 118, meshing with spur gear 119, and the spur gears118, 119 being of the same size, both shafts 34, 35 rotate at the samespeed.

The motor 86 may thus be operated at a relatively high rate of speed,such as the most eftlcient operating speed of the motor. In theembodiment illustrated, the speed reduction gear is adapted to reducethe speed in the ratio of nine to one, and with the speed control, whichis described in full hereinafter, the present device is adapted to beoperated at speeds of several hundred revolutions per minute to over.1500 revolutions per minute.

The motor shaft 130 is preferably provided with bearings 143 at eachend, which are capable of a limited universal movement to automaticallyalign. the bearings 143 with shaft 130 when the cover 104 is placed onthe casing 40. Each of these bearings may be substantially identical inform, and consequently, only one of the bearings is described in detail.v

For instance, the cover 104 is formed 'with a substantially cylindricalsocket 92 having an annular groove 144 located near the mouthof thesocket. A stamped annular sheet metal member 145, forming a smallportion of a sphere, is adapted to fit within the socket 92 with anoutwardly extending flange 146 in groove 144. The bearing 143 comprisesa sleeve 143 of bearing metal, which is provided with an annular flange147 at its outer end, and which is fixedly secured with a ball-shapedmetal member 148. The ball 148 fits within the spherical ^cup 145 andthe ange 147 may support a felt packing 149 adiacent an oil conduit 150.

All of the foregoingparts are secured in the socket 92 by an annularplate 151, which is secured in place by screw bolts 152, and which isprovided with an annular inwardly slopingflange 153 for engaging ball148. Any number of washers 154 may be interposed between pinion129 andbearing 143, and the plate 151 is preferably provided with a stampeddepression for engaging in a slot 155 to permit universal movement ofball 148, but to prevent rotation of the ball. The plate 151 is alsopreferably formed with slots 156 extending into said plate from itsouter edge about each screw bolt 152, so that the plate is secured inplace by screws passing through resilient tongues formed on plate 151.

Referring to Figs. 5 and 7, it will be observed that the side walls 93,94 of motor casing 40 are provided with inwardly projecting andtransversely extending ribs or formations 157, the lugs on each wallbeing provided with an inner cylindrical surface 158 which iscomplementary in shape t'o the outer surface of the motor field core159.

The provision of the inner cylindrical surfaces for supporting the motorfield core, enables the accurate location of the field core with respectto the armature so that a high degree of uniformity is attained in theair gap between the field core and the armature under the ordinaryconditions of manufacture and a high quality of motor structure may thusbe produced more economically.

At the points 160 on each rib 157, a definite shoulder is formed againstwhich the motor field core 159 rests and the field core may be securedin place by screw bolts and washers 161 threaded in bores 162 in the endof lugs or ribs 157. The motor field core 159 is preferably constructedof a multiplicity of laminations of soft iron, or similar materialhaving high magnetic properties, each lamination being a substantiallyannular metal plate formed with two inwardly projecting pole pieces 163,164, the pole pieces being widened at their ends to form grooves 165'forreceiving the eld windings 166, 167. Each of the field windings 166consists of a coil of a plurality of turns of relatively heavy insulatedwire adapted to carry full load current, since the present device ispreferably provided with a series motor.

The field windings are preferably arranged in coils and coveredwith tapeinsulation before their assembly on the iield core 159 and the coilsarev large enough so thatthey will pass over the projecting edges of thepole pieces 163, 164. After locating the field coil inside of the eldcore, the coil is pressed into the grooves 165 and brought to theconformation shown in Fig. 5 by curving the lateral portions of the coiloutward on the core, and drawing the inner parts of the coil .into thegrooves 165. The two ends of the coil may also be secured in place by acord which loops about the coil at each end and passes outside of thefield core 159 to draw the coil into the grooves 165.

The armature 144 also comprises a plurality of laminations of soft iron,or other magnetic material, all of which are provided with registeringrecesses 174 and slots 175 leading to the outside of the armature. Theelongated recesses 174 are adapted to receive the armature coils 176,consisting of a plurality of turns of insulated copper wire, the wirebeing retained in recesses 174 by strips of insulation 176 slid endwiseinto recesses 174 to close the slots 175. 'I'he ends of the respectivearmature coils 176 are connected to the insulated segments 177 ofacommutator 178, fixedly supported on shaft 130, and the commutator 178is adapted to be engaged by the oppositely disposed brushes 169,

` Any compact form of series winding may be used for the amature coils176, and wire provided with lacquer insulation is preferably employed toreduce the size of the armature and increase its efficiency. The shaft130 also supports a fan 179, consisting of a sheet metal plate having aplurality of radially extending armatures 180 with inwardly turnedblades 181.

The casing 40 and cover 104 are also provided with a plurality ofventilation openings 182 -located about each end of the shaft in thefront and rear walls, and these walls may also be provided withventilation openings 183 adjacent the top to provide ventilation for therheostat 87.

The side walls`93, 94 are provided with bores 184 at pointsdiagrammatically opposite each other with respect to the commutator178., and the bores 184 support bakelite tubes 185 for insulating thebrushes 169, 172. The bakelite tubes 185 are each molded about a sheetmetal tube 186, having a crimped end 187 to provide anchoringformations, and the metal sleeves are provided with annular flanges 188at the inner end, the sleeves 188 projecting sufficiently from theinsulating bushings 185 to form a connector The brushes 169, 172 mayconsist of carbon rods, each formed with a small head 190, about whichone end of a helical spring 191 may be engaged. The insulating bushings185 are provided with internal threads 192, and an insulating screw plug193 is threaded in the end of each bushing 185 to compress the helicalsprings 191 and maintain the brushes 169, 172 in engagement withcommutator 178. The connectors 189 are peculiarly adapted to receive theresilient clamping lingers 194 of connectors carried by conductorsleading from the field coils 166, 167.

The speed control device 87 preferably consists of a series rheostat,including a plurality of resistance windings 195, the various turns ofwhich may be successively connected in series with the armature andfield circuit of motor 86 by a movable switch arm 196.

Referring to Fig. 7, it will be observed that the Side walls 93 and 94are each provided with transversely extending ribs 197 adjacent the top,the ribs 197 having longitudinal slots 198 for slidably receiving theedges 199 of an insulating support 200 for rheostat 87.

The insulating support 200 mayconsist of a molded porcelain member orplate of substantially rectangular form preferably provided withupwardly projecting and downwardly projecting :danges 201 at each end toform a barrier between the contacts and other metallic parts of therheostat, and the casing 40. The rheostat is retained in its guides 198by engagement of the flanges 107 of the cover with the edges 199 of theporcelain.

The porcelain supporting plate 200 of rheostat 87 is provided with aplurality of apertures 202, located in two series along two concentricarcs, and the apertures 200 provide means for securing a plurality ofrheostat contacts 203, each of which consists of a sheet metal cup orhead, having a pair of downwardly extending prongs 204 for clamping thecontact to the porcelain.

The resistance windings 195 consist of a plurality of spaced turns ofresistance wire, and the contact bodies 204 form contact with the turns195 by the engagement of the lower sides 205 of contacts 203 withadjacent turns of the coils 195.

The last contact 173 is preferably provided with a downwardly extendingmetal 'flange 206 provided with a screw 207, forming a connector forconnection with one of the supply conductors. The porcelain body200 isalso provided with an upwardly projecting lug 208 for supporting anelongated'metal strip 171 forming one of the contacts of the rheostat87.

The elongated metal strip 171 has one end supported in a recess 209formed in a flange 201, and the opposite end is bent downward and passesthrough an aperture in the porcelain body 200, t0 form a connector 210,provided with a screw 211. The metal strip 171 is also provided with apunched tongue 212, which is bent downward through another aperture inporcelain body l0 and bent into engagement with the bottom of .theporcelain body to secure the elongated contact strip 171 on theporcelain body 2 00.

The upper wall 69 of casing 40 is provided lwith a centrally locatedbore 213 for receiving an insulating thumb piece 214, and the thumbpiece 214 is provided with a portion 215 of reduced diameter, forming ashoulder 216 for engaging the top of the casing. The thumb piece 214 ispreferably provided with a screw bolt 217, having its head molded in thethumb piece 214, and having a flattened lower portion for nonrotatablysupporting a movable contact 196. An insulating washer 218 is interposedbetween the movable Contact 196 and the casing wall 89, and the contact196 is secured on bolt 217 by a nut 219.

Referring to Fig. 2, it will be observed that one end of contact arm 196is provided with .a contact rivet 220, having a curved face for slidablyengaging the contact bodies 203, 173, and the opposite end 221 'oicontact arm 196 is adapted to engage the elongated strip contact 171.The porcelain body 200 is also provided at one side with a porcelainprojection 222, simulating the shape of a contact 203 and adapted toserve as a dead contact for the oil-position of the switch arm 196.

The nameplate 223 may be interposed between the thumb piece 214 andcasing wall 89, and the wall or nameplate is preferably provided withindicia, such as on or 011 with appropriate arrows, or a scale .forindicating the various positions of,4 switch arm 196.

One end of coil 166 is connected to one of the wires leading to thesupply conductors 168, while the other end of coil 166 is connected toone of a' pair of brushes 169. One end of coil 167 is con-- nected byconductor 170 to the elongated xed contact 171 of the rheostat 87, andthe other end of coil 167 is connected ,by a conductor to brush 172. Thelast Contact '173 of a series of rheostat contacts is theother terminalof the rheostat which is connected to the other wire of the supplyconductors 168.

It will thus be observed that the rheostat 87,

eld coils 166, 167, and armature coils 176 are adapted to be connectedin series by means of the switch arm 196, and when the switch arm 196rests on the dead contact 222, the circuit is broken through all threeof these elements.

Since one end of the motor circuit is connected by conductor 170 to oneend of the elongated xed contact 171, the movable contact 196, whichengages the strip 171, is adapted to connect in the circuit variousturns of the resistance wire 195, depending upon engagement of thecontact 220 with the various rheostat buttons 203. When the contact 220is in engagement with the upper rheostat contact 203 in Fig. 6, theentire set of resistance windings 196 is in circuit, so that the secondpositionof the thumb piece 214 provides the slowest rate of speed. 'Whenthe coniact 220 is moved to the position to engage the second rheostatcontact 203A, one-fourth of the resistance wire 195 is cut out, andthree-fourths of the rheostat resistance is in circuit, and so forth.When the contact 220 has reached the last rheostat contact 173, all ofthe resistance is cut out, and the motor operates at its highest speed.

The mechanical operation of the foregoing food mixer will be evidentfrom the foregoing description and statement of the functions of thevarious parts. However, the present combination of series rheostatcontrol, series motor and speed reduction device are particularlyeffective for the purpose of providing a food mixer or household powerunit having a wide range of adaptability and speed control for variouspurposes.

The series commutator motor is capable of operation on either direct oralternating current at ordinary lighting circuit voltages, and thecharacteristics of the motor are such that the motor is equallyadaptable to mashing potatoes or mixing heavy batter at slow speeds asit is to the high speed mixing of relatively thin liquids or material tobe whipped.

When the mixer is used in a relatively thick batter, the increasedresistance tends to decrease the speed of the motor, which decreases thecounter-electromotive force generated in the armature, and the motortakes an increased current, providing the necessary power for mixing therelatively thick batter.

While the motor has the inherent capability of decreasing its speedconsiderably under conditions of such an increased load, the bestoperation is secured by the use of the series rheostat, which furtherdecreases the speed of the motor and gives a relatively powerful mixingdevice which operates at a very low speed when mixing heavy or thickbatters.

Since the rheostat is in series with the motor, when an increased loadis placed upon the series motor having a series rheostat, the increasedcurrent makes a larger potential drop across the rheostat, andconsequently, reduces the effective voltage on the motor. This reductionin the voltage impressed on the motor gives a proportional reduction inspeed which also gives a decreased counter-electromotive force andfurther results in increased current with increased power and slowerspeed.

The various steps provided on the rheostat are thus adapted to provide amuch Wider range of speed control than wouldbe provided by a rheostatwith any other arrangement, and the present food mixer has been found tobe peculiarly effective and adaptable to all kinds of mixing, performingmany operations which have heretofore not been possible with any motordriven food mixer.

It has already been pointed out that the motor unit is compact, light,capable of use with all kinds of motor driven household appliances andeconomical in its manufacture and assembly.

The inclusion of the series rheostat, series motor, and speed reductionmechanism in the single unitary casing enables the provision of a smalland portable power unit for household appliances which has a high degreeof flexibility and which is perfectly adapted to be used for driving allkinds of domestic devices.

lWhile I have illustrated a preferred embodiment of my invention, manymodifications may be made without departing from the spirit of theinvention, and I do not wish to be limited to the precise details ofconstruction set forth, but desire to avail myself of all changes withinthe scop'eof the appended claims.

Having thus described my invention, what I claim is new and desire tosecure by Letters Patent of the United States, is:

1. In a motor unit for household appliances, the combination of a casinghaving substantially rectangular sides and having a separable cover,bearings carried by said casing and cover, an armature having ahorizontal shaft rotatably mounted in said bearings, said casing havinginwardly projecting lugs forming a round field core support, a fieldcore having an outer cylindrical surface for engaging said lugs, a pairof vertically extending power shafts, rotatably mounted in said casingand operative mechanical connections between said power shafts andarmature shaft in said casing.

2. In a motor unit for household appliances, the combination of a casinghaving substantially rectangular sides and having a separable cover, apower shaft rotatably mounted in the bottom of said casing, a motorstructure having an armature shaft rotatably mounted in said casing andcover, speed reduction gearing connecting 'said shafts, guides formed onthe inside of the walls of said casing, and a rheostat slidably mountedin said guides on said casing and confined in place by said cover.`

3. In a motor unit for household appliances, the combination of a casinghaving substantially rectangular sides and having -a separable cover, apower shaft rotatably mounted in the bottom of said casing, a motorstructure having an armature shaft rotatably mounted in said casing andcover, speed reduction gearing connecting said shafts, guides formed onthe inside of the walls of said casing, a rheostat slidably mounted insaid guides on said casing and confined in place by said cover, aninsulating actuating knob rotatably mounted in said casing and arheostat arm carried by the inner end of said arm.

4. In a motor unit for household appliances, the combination of a casinghaving substantially rectangular sides and' having a separable cover, apair of power shafts rotatably mounted in one end of said casing, amotor in said casing, a rheostat in said casing, a rheostat switch armhaving an insulating knob projecting from the top of said casing forcontrolling said motor, and a pair of insulating handles having cornerengaging formations engageable with the corner contour of said casingand secured thereto.

5. In a motor unit for household appliances the combination of a motorcasing with a series electric motor in said casing, a rheostatcomprising an insulating base removably mounted in said casing andconnected in series with the field and armature of said series motor, aninsulating knob rotatably mounted in the wall of said casing and havinga. movable contact arm located in said casing, a multiplicity ofcontacts carried by said rheostat for engagement with said arm, one oi'said contacts being adapted to effect continuous engagement with saidarmand others of said contacts being connected to spaced turns ofresistance wire on said rheostat, a pair of drive shafts rotatablymounted in the wall of said casing opi posite to said insulating knob,and speed reduc- 13,5 ing gearing connecting said motor and said driveist ' shafts.

' armature of said series motor, an insulating mob rotatably mounted inthe wall of said casing and having a movable contact arm located in saidcasing, a multiplicity of contacts carried by said rheostat forengagement with said arm, one of said contacts being adapted to effectcontinuous' engagement with said arm and others of said con- 15( tactsbeing connected to spaced turns of resistance wire on said rheostat, apair of drive shafts rotatably mounted inthe wall of said casingopposite to said insulatingv knob, speed reducing gearing connectingsaid motor and said drive shafts, said motor casing being provided withVentilation apertures located adjacent said rheostat and a fan driven bythe motor shaft and adapted to effect forced ventilation through saidcasing about said rheostat.

7. In a motor unit for household appliances th'e combination of alsubstantially rectangular casing with a motor unit located in saidcasing, a pair of drive shafts rotatably mounted in one Wall of saidcasing, a motor speed control device located in said casing and having acontrol member carried by the Wall opposite to said drive shaft, -and apair of double ended handles. said handles being located on the oppositeWalls of said casing and .each handle having both of its ends secured tosaid casing.

8. In a motor unit for household appliances the combination of asubstantially rectangular casing with a motor unit located in saidcasing, a pair of drive shafts rotatably mounted in one Wall of saidcasing, a motor speed control device located in said casing and having acontrol member carried by the wall opposite to said drive shaft, a pairof double ended handles, said handles being located on the oppositeWalls of said casing and each handle having both of its ends secured tosaid casing, said .casing being formed with outwardly projecting lugssurrounding said drive shafts, a supporting plate adapted to cover saidlugs, and a pair of auxiliary tubular shafts rotatably mounted on-saidsupporting plate and adapted to engage said drive shafts.

9. In a food mixer motor unit, the combination of a casing with aseries-wound motor therein, a pair of drive shafts of unequal lengthcarried by one of the walls of said casing and adapted for conjointrotation, operative mechanical gear reducing connections on the interiorof said casing between said motor and said drive shafts, said driveshafts protruding to the exterior of said casing and being adapted forself-aligned connection to driven members, said casing having a flangedportion adjacent said shafts on the exterior of said casing tofacilitate such connection, a variable resistor in series connectionwith said motor in said casing to control the speed and power availableat said shafts, said casing being provided with ventilation openings andfan means actuated by said motor effecting forced ventilation throughsaid casing.

ALBERT F. DORMEYER.

